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United States Patent |
5,290,651
|
Ong
|
March 1, 1994
|
Toner compositions with zinc complex charge enhancing additives
Abstract
A negatively charged toner composition comprised of a polymer resin or
polymer resins, colorants comprised of pigment particles and/or dyes,
optional surface additives, and a nonionic zinc complex charge enhancing
additive containing two different ligands derived from an
ortho-hydroxyphenol and an ortho-hydroxybenzoic acid.
Inventors:
|
Ong; Beng S. (Mississauga, CA)
|
Assignee:
|
Xerox Corporation (Stamford, CT)
|
Appl. No.:
|
964541 |
Filed:
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October 21, 1992 |
Current U.S. Class: |
430/108.3; 430/108.24 |
Intern'l Class: |
G03G 009/083 |
Field of Search: |
430/110,106.6
|
References Cited
U.S. Patent Documents
4206064 | Jun., 1980 | Kiuchi et al. | 430/106.
|
4298672 | Nov., 1981 | Lu | 430/108.
|
4411974 | Oct., 1983 | Lu et al. | 430/106.
|
4845003 | Jul., 1989 | Kiriu et al. | 430/110.
|
5153089 | Oct., 1992 | Ong et al. | 430/110.
|
Primary Examiner: Rodee; Christopher
Attorney, Agent or Firm: Palazzo; E. O.
Claims
What is claimed is:
1. A negatively charged toner composition comprised of a polymer resin or
polymer resins, colorants comprised of pigment particles and/or dyes,
optional surface additives, and a nonionic zinc complex charge enhancing
additive containing two different ligands derived from an
ortho-hydroxyphenol and an ortho-hydroxybenzoic acid.
2. A toner composition in accordance with claim 1 wherein the charge
additive is present in an amount of from about 0.05 to about 10 weight
percent.
3. A toner composition in accordance with claim 1 wherein the charge
additive is present in an amount of from about 0.05 to about 3 weight
percent.
4. A toner composition in accordance with claim 1 wherein the polymer is
selected from the group consisting of styrene polymers, styrene acrylic
polymers, styrene methacrylic polymers, polyesters, and mixtures thereof.
5. A toner composition in accordance with claim 1 wherein the colorants are
carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, red,
blue, green, brown pigments, or mixtures thereof.
6. A negatively charged toner composition comprised of polymer, pigment,
optional surface additives, and a zinc complex charge enhancing additive
represented by either of the two following formulas
##STR2##
wherein R, R', R", and R'" are independently selected from the group
consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, halogen, amino, and
hydroxy.
7. A toner composition in accordance with claim 6, wherein the charge
additive is selected from the group consisting of
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc,
(4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc,
(catecholato-3,5-di-tert-butylsalicylato)zinc,
(4-tert-butylcatecholato-4-hydroxysalicylato)zinc,
(4-tert-butylcatecholato-3,5-diisopropylsalicylato)zinc,
(4-tert-butylcatecholato-5-iodosalicylato)zinc,
(4-tert-butyl-catecholato-5-bromosalicylato)zinc,
(4-tert-butyl-catecholato-4-methylsalicylato)zinc,
(4-tert-butyl-catecholato-3-methylsalicylato)zinc,
(4-tert-butyl-catecholato-3-methoxysalicylato)zinc, and
(4-tert-butyl-catecholato-3,5-diiodosalicylato)zinc.
8. A toner composition in accordance with claim 7 wherein the charge
additive is present in an amount of from about 0.05 to about 10 weight
percent.
9. A toner composition in accordance with claim 7 wherein the toner polymer
is comprised of styrene polymers, acrylic or methacrylic polymers,
polyesters, or mixtures thereof.
10. A toner composition in accordance with claim 7 wherein styrene polymers
or polyesters are selected as the toner polymer.
11. A toner composition in accordance with claim 6 wherein R, R', R", and
R'" are selected from the group consisting of hydrogen, methyl, methoxy,
tertiary-butyl, bromine, and iodine.
12. A toner composition in accordance with claim 6 wherein
(tert-butylcatecholato-di-tert-butylsalicylato)zinc, or
(tert-butyl-catecholato-diiodosalicylato)zinc, or
(tert-butyl-catecholato-methoxysalicylato)zinc are selected as the charge
enhancing additive.
13. A toner composition in accordance with claim 6 with a negative
triboelectric charge of from between about -10 to about -40 microcoulombs
per gram.
14. (Amended) A toner composition in accordance with claim 6 wherein the
polymer is selected from the group consisting of styrene acrylates,
styrene methacrylates, and styrene butadienes.
15. A toner composition in accordance with claim 6 containing a wax
component which has a weight average molecular weight of from about 1,000
to about 7,000.
16. A toner composition in accordance with claim 15 wherein the wax
component is selected from the group consisting of polyethylene and
polypropylene.
17. A toner composition in accordance with claim 2 wherein the surface
additives are metal salts of a fatty acid, colloidal silicas, or mixtures
thereof.
18. A toner composition in accordance with claim 6 wherein the pigment is
carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, red,
blue, green, brown pigments, or mixtures thereof.
19. A toner in accordance with claim 6 wherein halogen is chlorine,
bromine, or iodine; alkyl and alkoxy contain from 1 to about 10 carbon
atoms; and aryl contains from 6 to about 24 carbon atoms.
20. A toner in accordance with claim 2 wherein aryl is phenyl or tolyl.
21. A developer composition comprised of a negatively charged toner
composition comprised of a polymer resin or polymer resins, colorants
comprised of pigment particles and/or dyes, optional surface additives,
and a nonionic zinc complex charge enhancing additive containing two
different ligands derived from an ortho-hydroxphenol and an
ortho-hydroxybenzoic acid; and carrier particles.
22. A developer composition comprised of a negatively charged toner
composition comprised of polymer, pigment, optional surface additives, and
a zinc complex charge enhancing additive represented by either of the two
following formulas
##STR3##
wherein R, R', R", and R'" are independently selected from the group
consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, halogen, amino, and
hydroxy; and carrier particles.
23. A developer composition in accordance with claim 22 wherein the carrier
particles are selected from the group consisting of ferrites, steel, and
an iron powder with a polymer or mixture of polymers coating thereover.
24. A developer composition in accordance with claim 23 wherein the coating
is selected from the group consisting of a methyl terpolymer, a
polyvinylidine fluoride, a polymethyl methacrylate, and a mixture of
polymers not in close proximity in the triboelectric series.
Description
BACKGROUND OF THE INVENTION
The invention is generally directed to toner and developer compositions,
and more specifically, the present invention is directed to developer and
toner compositions containing charge enhancing additives, which impart or
assist in imparting a negative charge to the toner particles and enable
toners with rapid triboelectric charging characteristics. In embodiments,
there are provided in accordance with the present invention toner
compositions comprised of a polymer or polymer resins, color pigment
particles or dye molecules, and certain zinc complex charge enhancing
additives containing mixed ligands derived from ortho-hydroxybenzoic acid
and ortho-hydroxyphenol. In embodiments, the present invention is directed
to toners with certain zinc complex charge enhancing additives, which
additives are obtained from the reaction of an ortho-hydroxybenzoic acid
and a base with an aqueous zinc ion solution containing an
ortho-hydroxyphenol. The zinc complex charge enhancing additives in
embodiments are believed to be nonionic in nature and comprised of two
different ligands, one ortho-hydroxybenzoic acid and one
ortho-hydroxyphenol, chelating to the central zinc atom. The
aforementioned charge additives in embodiments of the present invention
enable, for example, toners with rapid triboelectric charging
characteristics, extended developer life, stable triboelectrical
properties irrespective of changes in environmental conditions, and high
image print quality with substantially no background deposits. Also, the
aforementioned toner compositions usually contain a colorant component
comprised of, for example, carbon black, magnetites, or mixtures thereof,
color pigments or dyes with cyan, magenta, yellow, blue, green, red, or
brown color, or mixtures thereof thereby providing for the development and
generation of black and/or colored images. The toner and developer
compositions of the present invention can be selected for
electrophotographic, especially xerographic, imaging and printing
processes, including color processes.
Toners with negative charge additives are known, reference for example U.S.
Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally
incorporated herein by reference. The '974 patent discloses negatively
charged toner compositions comprised of resins, pigment particles, and as
a charge enhancing additive ortho-halophenyl carboxylic acids. Similarly,
there are disclosed in the '064 patent toner compositions with chromium,
cobalt, and nickel complexes of salicylic acid as negative charge
enhancing additives. In U.S. Pat. No. 4,845,003 there are illustrated
negatively charged toners with certain aluminum salt charge additives.
More specifically, this patent discloses as charge additives aluminum
complexes comprised of two or three hydroxybenzoic acid ligands bonded to
a central aluminum ion. While these charge additives may have the
capability of imparting negative triboelectric charge to toner particles,
they are generally not efficient in promoting the rate of triboelectric
charging of toner particles. A fast rate of triboelectric charging is
particularly crucial for high speed xerographic machines since, for
example, these machines consume toner rapidly, and fresh toner has to be
constantly added. The added uncharged toners, therefore, must charge up to
their equilibrium triboelectric charge level rapidly to ensure no
interruption in the xerographic imaging or printing operation. Another
shortcoming of these charge additives is their thermal instability, that
is they often break down during the thermal extrusion process of the toner
manufacturing cycle. Most or many of these and other disadvantages are
eliminated, or substantially eliminated with the zinc complex charge
additives of the present invention.
Developer compositions with charge enhancing additives, which impart a
positive charge to the toner particles, are also well known. Thus, for
example, there is described in U.S. Pat. No. 3,893,935 the use of
quaternary ammonium salts as charge control agents for electrostatic toner
compositions; U.S. Pat. No. 4,221,856 which discloses electrophotographic
toners containing resin compatible quaternary ammonium compounds in which
at least two R radicals are hydrocarbons having from 8 to about 22 carbon
atoms, and each other R is a hydrogen or hydrocarbon radical with from 1
to about 8 carbon atoms, and A is an anion, for example sulfate,
sulfonate, nitrate, borate, chlorate, and the halogens such as iodide,
chloride and bromide, reference the Abstract of the Disclosure and column
3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a
division of U.S. Pat. No. 4,291,111; similar teachings are presented in
U.S. Pat. No. 4,291,112 wherein A is an anion including, for example,
sulfate, sulfonate, nitrate, borate, chlorate, and the halogens; U.S. Pat.
No. 4,338,390, the disclosure of which is totally incorporated herein by
reference, discloses developer compositions containing as charge enhancing
additives organic sulfate and sulfonates, which additives can impart a
positive charge to the toner composition; U.S. Pat. No. 4,298,672, the
disclosure of which is totally incorporated herein by reference, discloses
positively charged toner compositions with resins and pigment particles,
and as charge enhancing additives alkyl pyridinium compounds.
Disclosed in copending patent applications U.S. Ser. No. 894,688 and U.S.
Ser. No. 894,690 are toner and developer compositions containing metal
complex charge additives which are anionic in nature, the disclosures of
which are totally incorporated herein by reference. More specifically,
disclosed in these copending patent applications is a negatively charged
toner composition comprised of a polymer or polymer resins, a colorant or
colorants, optional surface additives, and a metal complex charge
enhancing additive obtained from the reaction of a hydroxybenzoic acid and
a base with a mixture of a metal ion and a hydroxyphenol; and a negatively
charged toner composition comprised of a polymer or polymers, a colorant
or colorants, optional surface additives, and a metal complex charge
enhancing additive obtained from the reaction of a hydroxybenzoic acid and
a base with a mixture of a metal ion and an aromatic dicarboxylic acid.
These complexes are comprised of an anion with two bidentate ligands
chelating to a central metal, and countercations of protons, alkaline
metal ions, ammonium ions, and the like.
Although many charge enhancing additives are known, there continues to be a
need for charge enhancing additives which, when incorporated in toners,
provide toners with many of the advantages illustrated herein. There is
also a need for negative charge enhancing additives which are useful for
incorporation into black and colored toner compositions which can be
utilized for developing positive electrostatic latent images. Moreover,
there is a need for colored toner compositions containing charge enhancing
additives which do not interfere with the color quality of the colorants
present in the toners. Another need relates to the provision of toner
compositions with certain charge enhancing additives, which toners in
embodiments thereof possess substantially stable triboelectric charge
levels, and display acceptable rates of triboelectric charging
characteristics. Furthermore, there is also a need for toner compositions
with certain charge enhancing additives which possess excellent
dispersibility characteristics in toner resins, and can, therefore, form
stable dispersions in the toner compositions. There is also a need for
negatively charged black and colored toner compositions that are useful
for incorporation into various imaging processes, inclusive of color
xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of
which is totally incorporated herein by reference; laser printers; and
additionally a need for toner compositions useful in imaging apparatuses
having incorporated therein layered photoresponsive imaging members, such
as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of
which is totally incorporated herein by reference. Also, there is a need
for negative toner compositions which have desirable triboelectric charge
levels of, for example, from between about -10 to about -40 microcoulombs
per gram, and preferably from about -10 to about -25 microcoulombs per
gram, and triboelectric charging rates of less about 120 seconds, and
preferably less than 60 seconds as measured by standard charge
spectrograph methods when the toners are frictionally charged against
suitable carrier particles via conventional roll milling techniques. There
is also a need for environmentally compatible charge enhancing additives
which when incorporated at effective concentrations of, for example, less
than 10 weight percent, preferably less than 5 weight percent in toners,
provide toners that are environmentally acceptable. An additional need
resides in the provision of simple and cost-effective preparative
processes for the zinc complex charge enhancing additives of the present
invention. The concentrations of the charge additives that can be
incorporated into the toner compositions generally range from about 0.05
weight percent to about 10 weight percent, depending on whether the charge
additive is utilized as a surface additive or as a dispersion in the bulk
of the toner. The effective concentrations of toner in the developer, that
is toner and carrier particles, are, for example, from about 0.5 to about
5 weight percent, preferably from about 1 to about 3 weight percent.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide toner and developer
compositions with negative charge enhancing additives.
In another object of the present invention there are provided negatively
charged toner compositions useful for the development of electrostatic
latent images including color images.
In yet a further object of the present invention there may be provided, it
is believed, humidity insensitive, from about, for example, 20 to 80
percent relative humidity at temperatures of from 60.degree. to 80.degree.
F. as determined in a relative humidity testing chamber, negatively
charged toner compositions with desirable triboelectric charging rates of
less than 120 seconds, and preferably less than 60 seconds as determined
by the charge spectrograph method, and acceptable triboelectric charging
levels of from about -10 to about -40 microcoulombs per gram.
Another object of the present invention resides in the preparation of
negative toners which will enable the development of images in
electrophotographic imaging apparatuses, which images have substantially
no background deposits thereon, are substantially smudge proof or smudge
resistant, and therefore, are of excellent resolution; and further, such
toner compositions can be selected for high speed electrophotographic
apparatuses, that is for example those exceeding 50 copies per minute.
A further object is to provide a simple and cost-effective process for the
preparation of zinc complex charge enhancing additives.
These and other objects of the present invention may be accomplished in
embodiments thereof by providing toner compositions comprised of a polymer
resin or polymer resins, colorants comprised of color pigment particles or
dye molecules, and certain zinc complex charge enhancing additives derived
from the reaction of an ortho-hydroxybenzoic acid and a base with an
aqueous zinc ion solution containing an ortho-hydroxyphenol. More
specifically, the present invention in embodiments is directed to toner
compositions comprised of polymer resins, pigment, or dye, and a negative
charge enhancing additive which may be represented by the formulas (I) and
(II)
##STR1##
wherein R, R', R", and R"' are independently selected from the group
consisting of hydrogen, alkyl with, for example, 1 to about 10 carbon
atoms, aryl with, for example, from 6 to about 24 carbon atoms such as
phenyl, tolyl, and the like, alkoxy and aryloxy with from 1 to about 12
carbon atoms, halogen like chlorine, bromine, amino, hydroxy, and the
like. Examples of alkyl, and alkoxy include known components with, for
example, 1 to about 10 carbon atoms, such as methyl, methoxy, ethyl,
ethoxy, propyl, propoxy, butyl, butoxy, pentyl, pentoxy, hexyl, hexoxy,
heptyl, heptoxy, and the like. Aryl and aryloxy include known substituents
such as phenyl, phenoxy, tolyl, methylphenoxy, naphthyl, naphthoxy, and
the like. Halogen includes chlorine, bromine, iodine, and fluorine.
The aforementioned charge additives can be incorporated into the toner, may
be present on the toner surface, or may be present on toner surface
additives such as colloidal silica particles. Advantages of rapid
triboelectric charging characteristics of generally less than 120 seconds,
and preferably less than 60 seconds in embodiments as measured by the
standard charge spectrograph methods when the toner particles are
frictionally charged against carrier particles by known conventional roll
mixing methods, appropriate triboelectric charge levels, and the like can
be achieved with many of the aforementioned toners of the present
invention. In another embodiment of the present invention, there are
provided, subsequent to known micronization and classification, toner
particles with a volume average diameter of from about 2 to about 20
microns.
The zinc complex charge additives of the present invention can be prepared
by the reaction of an ortho-hydroxybenzoic acid and a base with an aqueous
zinc ion solution containing an ortho-hydroxyphenol. Specifically, the
synthesis can be accomplished by a dropwise addition of an aqueous
solution of one molar equivalent of an ortho-hydroxybenzoic acid and two
or more molar equivalents of a base to a well stirred aqueous zinc sulfate
solution containing slight excess of an ortho-hydroxyphenol. The addition
is carried out over a period of from about 15 minutes to 2 hours, and the
zinc sulfate solution is retained at a temperature ranging from ambient to
about 90.degree. C. After the addition, the reaction mixture is stirred at
a temperature of from about 40.degree. C. to the refluxing temperature of
the reaction medium for another period of 15 minutes to several hours, for
example about 10 hours. The reaction product is then filtered, and washed
with dilute aqueous base, water, and then dried in a vacuum.
The toner compositions of the present invention can be prepared by a number
of known methods such as admixing and heating polymer resins such as
styrene butadiene copolymers, colorants such as color pigment particles or
dye compounds, and the aforementioned metal complex charge enhancing
additive, or mixtures of charge additives in a concentration preferably
ranging from about 0.5 percent to about 5 percent in a toner extrusion
device, such as the ZSK53 available from Werner Pfleiderer, and removing
the resulting toner composition from the device. Subsequent to cooling,
the toner composition is subjected to grinding utilizing, for example, a
Sturtevant micronizer for the purpose of achieving toner particles with a
volume average diameter of from about 2 to about 25 microns, and
preferably from about 3 to about 12 microns, which diameters are
determined by a Coulter Counter. Subsequently, the toner compositions can
be classified utilizing, for example, a Donaldson Model B classifier for
the purpose of removing unwanted fine toner particles.
Illustrative examples of suitable toner resins selected for the toner and
developer compositions of the present invention include vinyl polymers
such as styrene polymers, acrylonitrile polymers, vinyl ether polymers,
acrylate and methacrylate polymers; styrene acrylates, styrene
methacrylates, styrene butadienes; epoxy polymers; polyurethanes;
polyamides and polyimides; polyesters; and the like. The polymer resins
selected for the toner compositions of the present invention include
homopolymers or copolymers of two or more monomers. Furthermore, the above
mentioned polymer resins may also be crosslinked depending on the desired
toner properties. Illustrative vinyl monomer units in the vinyl polymers
include styrene, substituted styrenes such as methyl styrene,
chlorostyrene, methyl acrylate and methacrylate, ethyl acrylate and
methacrylate, propyl acrylate and methacrylate, butyl acrylate and
methacrylate, pentyl acrylate and methacrylate, butadiene, vinyl chloride,
acrylonitrile, acrylamide, alkyl vinyl ether and the like. Illustrative
examples of the dicarboxylic acid units in the polyester resins suitable
for use in the toner compositions of the present invention include
phthalic acid, terephthalic acid, isophthalic acid, succinic acid,
glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, maleic acid, fumaric acid, dimethyl glutaric acid,
bromoadipic acids, dichloroglutaric acids, and the like; while
illustrative examples of the diol units in the polyester resins include
ethanediol, propanediols, butanediols, pentanediols, cyclopentanediols,
bis(hydroxyphenyl)alkanes, dihydroxybiphenyl, substituted
dihydroxybiphenyls, and the like.
In embodiments, there are selected polyester resins derived from a
dicarboxylic acid and a diphenol, reference U.S. Pat. No. 3,590,000, the
disclosure of which is totally incorporated herein by reference; polyester
resins obtained from the reaction of bisphenol A and propylene oxide,
followed by the reaction of the resulting product with fumaric acid, and
branched polyester resins resulting from the reaction of
dimethylterephthalate with 1,3-butanediol, 1,2-propanediol, and
pentanetriol. Further low melting polyesters, especially those prepared by
reactive extrusion, reference U.S. Ser. No. 814,641, and U.S. Ser. No.
814,782, the disclosures of which are totally incorporated herein by
reference, can be selected as toner resins. Other specific toner resins
include styrene-methacrylate copolymers and styrene-butadiene copolymers;
PLIOLITES.RTM.; suspension polymerized styrene-butadienes, reference U.S.
Pat. No. 4,558,108, the disclosure of which is totally incorporated herein
by reference. Also, waxes with a molecular weight of from about 1,000 to
about 6,000, such as polyethylene, polypropylene, and paraffin waxes, can
be included in, or on the toner compositions as fuser roll release agents.
The toner resins are present in a sufficient, but effective amount, for
example from about 30 to about 95 weight percent. Thus, when 1 percent by
weight of the charge enhancing additive is present, and 10 percent by
weight of colorant, such as carbon black or color pigment, is contained
therein, about 89 percent by weight of resin is selected. Also, the charge
enhancing additive of the present invention may be applied as a surface
coating on the toner particles. When used as a coating, the charge
enhancing additive of the present invention is present in an amount of
from about 0.05 weight percent to about 5 weight percent, and preferably
from about 0.1 weight percent to about 1.0 weight percent.
Numerous well known suitable color pigments or dyes can be selected as the
colorant for the toner compositions including, for example, carbon black,
like REGAL 330.RTM., nigrosine dye, metal phthalocyanines, aniline blue,
magnetite, or mixtures thereof. The colorant, which is preferably carbon
black or other color pigments, should be present in a sufficient amount to
render the toner composition with a sufficiently high color intensity.
Generally, the colorants are present in amounts of from about 1 weight
percent to about 20 weight percent, and preferably from about 2 to about
10 weight percent based on the total weight of the toner composition;
however, lesser or greater amounts of colorant can be selected.
When the colorants are comprised of magnetites or a mixture of magnetites
and color pigment particles, thereby enabling single component toners and
toners for magnetic ink character recognition (MICR) applications in some
instances, which magnetites are a mixture of iron oxides (FeO.Fe.sub.2
O.sub.3) including those commercially available as MAPICO BLACK.RTM., they
are present in the toner composition in an amount of from about 5 weight
percent to about 60 weight percent, and preferably in an amount of from
about 10 weight percent to about 50 weight percent. Mixtures of carbon
black and magnetite with from about 1 to about 15 weight percent of carbon
black, and preferably from about 2 to about 6 weight percent of carbon
black, and magnetite, such as MAPICO BLACK.RTM., in an amount of, for
example, from about 5 to about 60, and preferably from about 10 to about
50 weight percent can be selected for black toner compositions of the
present invention.
There can also be blended with the toner compositions of the present
invention external additives including flow aid additives, which additives
are usually present on the surface thereof. Examples of these additives
include colloidal silicas, such as AEROSIL.RTM., metal salts and metal
salts of fatty acids inclusive of zinc stearate, aluminum oxides, cerium
oxides, titanium oxides, and mixtures thereof, which additives are
generally present in an amount of from about 0.1 percent by weight to
about 5 percent by weight, and preferably in an amount of from about 0.5
percent by weight to about 2 percent by weight. Several of the
aforementioned additives are illustrated in U.S. Pat. Nos. 3,590,000 and
3,800,588, the disclosures of which are totally incorporated herein by
reference.
With further respect to the present invention, colloidal silicas, such as
AEROSIL.RTM., can be surface treated with the metal complex charge
additives of the present invention illustrated herein in an amount of from
about 1 to about 50 weight percent and preferably 10 weight percent to
about 25 weight percent, followed by the addition thereof to the toners in
an amount of from 0.1 to 10 and preferably 0.1 to 5 weight percent.
Also, there can be included in the toner compositions of the present
invention low molecular weight waxes, such as polypropylenes and
polyethylenes commercially available from Allied Chemical and Petrolite
Corporation, EPOLENE N-15R.TM. commercially available from Eastman
Chemical Products, Inc., VISCOL 550-P.TM., a low weight average molecular
weight polypropylene available from Sanyo Kasei K. K., and similar
materials. The commercially available polyethylenes selected have a
molecular weight of from about 1,000 to about 1,500, while the
commercially available polypropylenes utilized for the toner compositions
of the present invention are believed to have a molecular weight of from
about 4,000 to about 5,000. Many of the polyethylene and polypropylene
compositions useful in the present invention are illustrated in British
Patent No. 1,442,835, the disclosure of which is totally incorporated
herein by reference. These low molecular weight wax materials are present
in the toner composition of the present invention in various amounts,
however, generally these waxes are present in the toner composition in an
amount of from about 1 percent by weight to about 15 percent by weight,
and preferably in an amount of from about 2 weight percent to about 10
weight percent.
Encompassed within the scope of the present invention are colored toner and
developer compositions comprised of toner resins, optional surface
additives, the charge enhancing additives illustrated herein, and as
colorants red, blue, green, brown, magenta, cyan and/or yellow dyes or
color pigments, as well as mixtures thereof. More specifically, with
regard to the generation of color images utilizing a developer composition
with the charge enhancing additives of the present invention, illustrative
examples of magenta colorants that may be selected include, for example,
2,9-dimethyl-substituted quinacridone and anthraquinone dye identified in
the Color Index as CI 60710, CI Dispersed Red 15, diazo dye identified in
the Color Index as CI 26050, CI Solvent Red 19, and the like. Illustrative
examples of cyan colorants that may be used include copper phthalocyanine,
x-copper phthalocyanine pigment listed in the Color Index as CI 74160, CI
Pigment Blue, and Anthrathrene Blue, identified in the Color Index as CI
69810, Special Blue X-2137, and the like; while illustrative examples of
yellow colorants that may be selected include diarylide yellow
3,3-dichlorobenzidene acetoacetanilides, a monoazo pigment identified in
the Color Index as CI 12700, CI Solvent Yellow 16, a nitrophenyl amine
sulfonamide identified in the Color Index as Foron Yellow SE/GLN, CI
Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilide
phenylazo-4'-chloro-2,5-dimethoxy acetoacetanilide, and Permanent Yellow
FGL. The aforementioned colorants are incorporated into the toner
composition in various suitable effective amounts providing the objectives
of the present invention are achieved. In one embodiment, these colorants
are present in the toner composition in an amount of from about 1 percent
by weight to about 15 percent by weight based on the total weight of the
toner.
For the formulation of developer compositions, there are mixed with the
toner particles carrier components, particularly those that are capable of
triboelectrically assuming an opposite polarity to that of the toner
composition. Accordingly, the carrier particles of the present invention
are selected to be those that would render the toner particles negatively
charged while acquiring a positive charge polarity themselves via
frictional charging against the toner particles of the present invention.
The opposite charge polarities of the carrier and toner particles of the
developer composition thus ensure the toner particles to adhere to and
surround the carrier particles. Illustrative examples of carrier particles
include iron powder, steel, nickel, iron, ferrites, including copper zinc
ferrites, nickel zinc ferrites, and the like. Additionally, there can be
selected as carrier particles nickel berry carriers as illustrated in U.S.
Pat. No. 3,847,604, the disclosure of which is totally incorporated herein
by reference. The selected carrier particles can be used with or without a
coating, the coating generally containing terpolymers of styrene,
methylmethacrylate, and a silane, such as triethoxysilane, reference U.S.
Pat. Nos. 3,526,533 and 3,467,634, the disclosures of which are totally
incorporated herein by reference; polymethyl methacrylates; other known
coatings; and the like. The carrier particles may also include in the
coating, which coating can be present in one embodiment in an amount of
from about 0.1 to about 3 weight percent, conductive substances such as
carbon black in an amount of from about 5 to about 30 percent by weight.
Polymer coatings not in close proximity in the triboelectric series can
also be selected, reference U.S. Pat. Nos. 4,937,166 and 4,935,326, the
disclosures of which are totally incorporated herein by reference,
including for example KYNAR.RTM. and polymethylmethacrylate mixtures
(40/60). Coating weights can vary as indicated herein; generally, however,
from about 0.3 to about 2, and preferably from about 0.5 to about 1.5
weight percent coating weight is selected.
Furthermore, the diameter of the carrier particles, preferably spherical in
shape, is generally from about 50 to about 1,000 microns, and preferably
from between about 80 and 200 microns in volume average diameter thereby
permitting them, for example, to possess sufficient density and inertia to
avoid adherence to the electrostatic images during the development
process. The carrier component can be mixed with the toner composition in
various suitable combinations, such as about 1 to about 5 parts of toner
by weight per 100 parts by weight of carrier.
The toner composition of the present invention can be prepared by a number
of known methods including extrusion melt blending the toner resins,
colorants, and the metal complex charge enhancing additive of the present
invention as indicated herein, followed by mechanical attrition and
classification. Other methods include those well known in the art such as
spray drying, melt dispersion, extrusion processing, dispersion
polymerization, and suspension polymerization. Also, as indicated herein
the toner composition without the charge enhancing additive can be first
prepared, followed by addition of the charge enhancing additives and other
optional surface additives, or the charge enhancing additive treated
surface additives such as colloidal silicas. Further, other methods of
preparation for the toner are as illustrated herein.
The toner and developer compositions of the present invention may be
selected for use in electrostatographic imaging apparatuses containing
therein conventional photoreceptors providing that they are capable of
forming positive electrostatic latent images relative to the triboelectric
charge polarity of the toners.
The toners of the present invention are usually jetted and classified
subsequent to preparation to enable toner particles with a preferred
volume average diameter of from about 2 to about 25 microns, and more
preferably from about 3 to about 12 microns. The triboelectric charging
rates for the toners of the present invention are preferably less than 120
seconds, and more specifically, less than 60 seconds in embodiments
thereof as determined by the known charge spectrograph method as described
hereinbefore. These toner compositions with rapid rates of triboelectric
charging characteristics enable, for example, the development of images in
electrophotographic imaging apparatuses, which images have substantially
no background deposits thereon, even at high toner dispensing rates in
some instances, for instance exceeding 20 grams per minute; and further,
such toner compositions can be selected for high speed electrophotographic
apparatuses, that is those exceeding 50 copies per minute.
Examples of specific charge additives of the present invention are as
illustrated herein and include
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc,
(4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc,
(catecholato-3,5-di-tert-butylsalicylato)zinc,
(4-tert-butylcatecholato-4-hydroxysalicylato)zinc,
(4-tert-butylcatecholato-3,5-diisopropylsalicylato)zinc,
(4-tert-butylcatecholato-5-iodosalicylato)zinc,
(4-tert-butyl-catecholato-5-bromosalicylato)zinc,
(4-tert-butyl-catecholato-4-methylsalicylato)zinc,
(4-tert-butyl-catecholato-3-methylsalicylato)zinc,
(4-tert-butyl-catecholato-3-methoxysalicylato)zinc, and
(4-tert-butyl-catecholato-3,5-diiodosalicylato)zinc.
The following Examples are being supplied to further illustrate various
embodiments of the present invention, it being noted that these Examples
are intended to illustrate and not limit the scope of the present
invention. Comparative Examples are also presented.
EXAMPLE I
The zinc charge enchancing additive,
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc, was prepared
according to the following procedure.
A mixture of 7.19 grams (25.0 millimoles) of zinc sulfate heptahydrate
[ZnSO.sub.4.7H.sub.2 O] and 4.99 grams (30.0 millimoles) of
4-tert-butylcatechol in 100 milliliters of water was mechanically stirred
and heated to 85.degree. to 90.degree. C. in a 1 liter round-bottomed
flask fitted with a water condenser. To this reaction mixture was added in
a dropwise fashion a solution of 3.30 grams of potassium hydroxide and
6.26 grams (25.0 millimoles) of 3,5-di-tert-butylsalicylic acid in 150
milliliters of water. The addition was accomplished at a rate of about 2
milliliters per minute over a period of about 75 minutes, and a grayish
white product was observed to precipitate out of solution throughout the
addition. Subsequently, the reaction mixture was further stirred at the
same temperature for another 2 hours, and then cooled down to about
50.degree. to 60.degree. C. before it was filtered. The grayish zinc
complex product was first washed with dilute aqueous potassium hydroxide
solution and then water, and was dried in vacuo at 75.degree. C. for 36
hours. The yield was 91 percent.
.sup.1 H-NMR (DMSO-d.sub.6 /TFA-d), .delta.(ppm): 1.16 (s, 9H); 1.22 (s,
9H); 1.34 (s, 9H); 6.5 to 6.8 (ABC, 3H); 7.4 to 7.7 (AB, 2H).
Elemental Analysis Calculated for: C.sub.25 H.sub.34 O.sub.5 Zn: C, 62.57;
H, 7.14; O, 16.67; Zn, 13.62. Found: C, 61.93; H, 6.85; O, 16.34; Zn,
12.79.
EXAMPLE II
The zinc charge enhancing additive,
(4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc, was prepared in
accordance with the procedure of Example I except that 4-methylcatechol
was utilized in place of 4-tert-butylcatechol. The yield of
(4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc was 87 percent.
EXAMPLE III
The zinc charge enhancing additive,
(4-tert-butylcatecholato-3,5-di-iodosalicylato)zinc, was prepared in
accordance with the procedure of Example I except that 3,5-diiodosalicylic
acid was utilized in place of 3,5-di-tert-butylsalicylic acid. The yield
of (4-tert-butylcatecholato-3,5-diiodosalicylato)zinc was 92 percent.
EXAMPLE IV
There was prepared in an extrusion device, available as ZSK-30 from Werner
Pfleiderer, a toner composition by adding thereto 94.0 weight percent of a
suspension polymerized styrene butadiene resin, reference U.S. Pat. No.
4,558,108, the disclosure of which is totally incorporated herein by
reference and 6.0 weight percent REGAL 330.RTM. carbon black. The toner
composition was extruded at a rate of 20 pounds per hour at a temperature
of about 130.degree. C. with a screw speed of 200 rpm. The strands of melt
mixed product exiting from the extruder were air cooled, pelletized in a
Berlyn Pelletizer and then fitzmilled in a Model J Fitzmill. The toner
product was then subjected to grinding in a Sturtevant micronizer.
Thereafter, the aforementioned toner particles were classifed in a
Donaldson Model B classifier for the purpose of removing fine particles,
that is those with a volume average diameter of less than 4 microns. The
resulting toner had a volume average particle diameter of 10.6 microns,
and a particle size distribution of 1.22 as measured by a Coulter Counter.
Subsequently, the toner was surface coated with 0.25 weight percent of
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc of Example I by
blending in a small coffee mill for 30 to 60 seconds.
The above treated toner was equilibrated at room temperature under a 50
percent relative humidity condition for 24 hours. A developer was then
prepared by blending 2.0 weight percent of the surface treated toner with
98.0 weight percent of a carrier containing a nickel zinc ferrite core
obtained from Steward Chemicals and 0.9 weight percent of a polymer
composite coating comprised of 80 weight percent of a methyl terpolymer
and 20 weight percent of VULCAN XC72R.RTM. carbon black. The methyl
terpolymer is comprised of about 81 weight percent of polymethyl
methacrylate and 19 weight percent of a styrene vinyltriethoxysilane
polymer. The developer was roll milled for 30 minutes to generate the time
zero developer, and the triboelectric charge of the toner of the resulting
developer was measured to be -28.6 microcoulombs per gram by the standard
blow-off technique in a Faraday Cage apparatus. To measure the rate of
triboelectric charging of toner, 1.0 weight percent of the uncharged toner
was added to the time zero developer, and the charge distribution of the
toner of the resulting developer was measured as a function of the
blending time via roll milling using a charge spectrograph. The time
required for the toner of the resulting developer to attain a charge
distribution similar to that of the toner of the time zero developer was
taken to be the rate of charging of the toner. For this toner, the rate of
charging was about 15 seconds.
COMPARATIVE EXAMPLE (A)
A comparative black toner with a commercial charge enhancing additive,
BONTRON E-88.TM. (obtained from Orient Chemicals), which is believed to be
an anionic complex of an anion of two 3,5-di-tert-butylsalicylic acid
ligands bonded to a central aluminum atom, and a countercation of proton
or alkaline metal ion was prepared by blending the untreated toner of
Example IV with 0.25 weight percent of BONTRON E-88.TM., and a developer
was then prepared from this toner in accordance with the procedure of
Example IV. The toner exhibited a triboelectric charge of -40.4
microcoulombs per gram, and its rate of charging was measured to be about
5 minutes.
EXAMPLE V
A black toner with (4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc of
Example II as a charge enhancing additive was prepared in accordance with
the procedure of Example IV except that 0.10 weight percent of
(4-methylcatecholato-3,5-di-tert-butylsalicylato)zinc was employed in
place of 0.25 weight percent of
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc as the charge
enhancing additive, and a developer was then prepared from this toner as
before. The toner has a triboelectric charge of -20.9 microcoulombs per
gram, and a charging rate of about 15 seconds.
COMPARATIVE EXAMPLE (B)
A comparative black toner with 0.10 weight percent of the commercial charge
enhancing additive, BONTRON E-88.TM. obtained from Orient Chemicals, was
prepared by blending the untreated toner of Example IV with 0.10 weight
percent of BONTRON E-88.TM., and a developer was then prepared from this
toner in accordance with the procedure of Example IV. The toner exhibited
a triboelectric charge level of -15.2 microcoulombs per gram, and its rate
of charging was measured to be about 5 minutes.
EXAMPLE VI
A black toner with 0.25 weight percent of
(4-tert-butylcatecholato-3,5-diiodosalicylato)zinc of Example III as a
charge enhancing additive was prepared in accordance with the procedure of
Example IV except that (4-tert-butylcatecholato-3,5-diiodosalicylato)zinc
was utilized instead of
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc. A developer was
then prepared from this toner in accordance with the procedure of Example
IV. The toner displayed a triboelectric charge of -31.2 microcoulombs per
gram, and its rate of charging was measured to be about 15 seconds.
COMPARATIVE EXAMPLE (C)
A comparative black toner with 0.25 weight percent of the commercial charge
enhancing additive, BONTRON E-84.TM. (obtained from Orient Chemicals),
which is believed to be comprised of an anion of two
3,5-di-tert-butylsalicylic acid ligands bonded to a central zinc atom, and
a countercation of proton or alkaline metal ion, was prepared by blending
the untreated toner of Example IV with 0.25 weight percent of BONTRON
E-84.TM., and a developer was then prepared from this toner in accordance
with the procedure of Example IV. The toner exhibited a triboelectric
charge of -25.6 microcoulombs per gram, and its rate of charging was
measured to be about 10 minutes.
EXAMPLE VII
A blue toner comprised of 97.0 weight percent of SPAR II polyester resin,
2.0 weight percent of PV FAST BLUE.TM. pigment, and 1.0 weight percent of
(4-tert-butylcatecholato-3,5-di-tert-butylsalicylato)zinc of Example I was
prepared by melt blending these three components, followed by micronizing
and classifying in accordance with the procedure of Example IV. The
resulting toner had a volume average particle diameter of 8.9 microns, and
a particle size distribution of 1.29. A developer was prepared from this
toner using 2.0 weight percent of toner and a carrier containing a steel
core and 0.8 weight percent of a polymer composite coating comprised of 80
weight percent of polymethyl methacrylate and 20 weight percent of VULCAN
XC72.TM. carbon black. The toner displayed a triboelectric charge of -16.7
microcoulombs per gram, and its rate of charging was measured to be about
60 seconds.
The toner was then surface coated with 0.5 weight percent of AEROSIL
R972.RTM. by a conventional dry blending method, and a developer was made
from this toner and the same carrier particles as before. The
triboelectric charge of this toner was measured to be -19.2 microcoulombs
per gram, and its rate of charging was 30 seconds.
COMPARATIVE EXAMPLE (D)
A comparative blue toner and developer composition with a commercial charge
additive, BONTRON E-84.TM., were prepared in accordance with the procedure
of Example VII except that BONTRON E-84.TM. was utilized in place of the
zinc complex charge additive of Example I. The toner displayed a
triboelectric charge of -10.5 microcoulombs per gram, and its rate of
charging was about 15 minute.
Other modifications of the present invention may occur to those skilled in
the art subsequent to a review of the present application, and these
modifications, including equivalents thereof, are intended to be included
within the scope of the present invention.
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